1. Field of the Invention
The present invention relates to a back-junction solar cell.
2. Description of the Background Art
In general, the so-called back-junction solar cell including a semiconductor layer on a back surface of a substrate is proposed.
In Japanese Patent Laying-Open No. 2005-101151, there is disclosed a photovoltaic device including a semiconductor substrate having a photoreceiving surface and a back surface, an i-type semiconductor layer formed on the back surface of the semiconductor substrate, a p-type semiconductor layer formed on a prescribed region of the surface of the i-type semiconductor layer and an n-type semiconductor layer formed to extend over the surface of the i-type semiconductor layer and the surface of the p-type semiconductor layer. The photovoltaic device described in Japanese Patent Laying-Open No. 2005-101151 is manufactured by plasma CVD through a step of forming the i-type semiconductor layer on the back surface of the semiconductor substrate, a step of forming the p-type semiconductor layer on the prescribed region of the surface of the i-type semiconductor layer and a step of forming the n-type semiconductor layer to extend over the surface of the i-type semiconductor layer and the surface of the p-type semiconductor layer.
In the case of manufacturing the photovoltaic device described in Japanese Patent Laying-Open No. 2005-101151 by plasma CVD, however, a p-type impurity contained in the p-type semiconductor layer desorbs from the layer due to plasma generated in the step of forming the n-type semiconductor layer to extend over the surface of the i-type semiconductor layer and the surface of the p-type semiconductor layer. The desorbing p-type impurity adheres to the surface of the p-type semiconductor layer and the surface of the i-type semiconductor layer. Consequently, the space between the semiconductor substrate and the n-type semiconductor layer is contaminated with the undesired p-type impurity, and hence there is a possibility that the characteristics of a solar cell lower, and there is such a problem that it is difficult to manufacture a solar cell having excellent solar cell characteristics with a high yield.
The present invention has been proposed in order to solve the aforementioned problem, and an object of the present invention is to provide a solar cell having excellent solar cell characteristics by suppressing contamination with an undesired impurity.